CtsBlockCipher
using Org.BouncyCastle.Utilities;
using System;
namespace Org.BouncyCastle.Crypto.Modes
{
public class CtsBlockCipher : BufferedBlockCipher
{
private readonly int m_blockSize;
public CtsBlockCipher(IBlockCipher cipher)
: this(EcbBlockCipher.GetBlockCipherMode(cipher))
{
}
public CtsBlockCipher(IBlockCipherMode cipherMode)
{
if (!(cipherMode is CbcBlockCipher) && !(cipherMode is EcbBlockCipher))
throw new ArgumentException("CtsBlockCipher can only accept ECB, or CBC ciphers");
m_cipherMode = cipherMode;
m_blockSize = cipherMode.GetBlockSize();
buf = new byte[m_blockSize * 2];
bufOff = 0;
}
public override int GetBlockSize()
{
return m_blockSize;
}
public override int GetOutputSize(int length)
{
return bufOff + length;
}
public override int GetUpdateOutputSize(int length)
{
return BufferedCipherBase.GetFullBlocksSize(bufOff + length - 1, buf.Length);
}
public override int ProcessByte(byte input, byte[] output, int outOff)
{
int result = 0;
if (bufOff == buf.Length) {
Check.OutputLength(output, outOff, m_blockSize, "output buffer too short");
result = m_cipherMode.ProcessBlock(buf, 0, output, outOff);
Array.Copy(buf, m_blockSize, buf, 0, m_blockSize);
bufOff = m_blockSize;
}
buf[bufOff++] = input;
return result;
}
public override int ProcessBytes(byte[] input, int inOff, int length, byte[] output, int outOff)
{
if (length < 1) {
if (length < 0)
throw new ArgumentException("Can't have a negative input length!");
return 0;
}
int num = 0;
int num2 = buf.Length - bufOff;
if (length > num2) {
int updateOutputSize = GetUpdateOutputSize(length);
Check.OutputLength(output, outOff, updateOutputSize, "output buffer too short");
Array.Copy(input, inOff, buf, bufOff, num2);
inOff += num2;
length -= num2;
if (output == input && Arrays.SegmentsOverlap(outOff, m_blockSize, inOff, length)) {
input = new byte[length];
Array.Copy(output, inOff, input, 0, length);
inOff = 0;
}
num = m_cipherMode.ProcessBlock(buf, 0, output, outOff);
Array.Copy(buf, m_blockSize, buf, 0, m_blockSize);
bufOff = m_blockSize;
while (length > m_blockSize) {
num += m_cipherMode.ProcessBlock(buf, 0, output, outOff + num);
Array.Copy(input, inOff, buf, 0, m_blockSize);
inOff += m_blockSize;
length -= m_blockSize;
}
}
Array.Copy(input, inOff, buf, bufOff, length);
bufOff += length;
return num;
}
public override int DoFinal(byte[] output, int outOff)
{
try {
Check.DataLength(bufOff < m_blockSize, "need at least one block of input for CTS");
Check.OutputLength(output, outOff, bufOff, "output buffer too short");
if (forEncryption) {
m_cipherMode.ProcessBlock(buf, 0, buf, 0);
for (int i = bufOff; i < buf.Length; i++) {
buf[i] = buf[i - m_blockSize];
}
for (int j = m_blockSize; j < bufOff; j++) {
buf[j] ^= buf[j - m_blockSize];
}
m_cipherMode.UnderlyingCipher.ProcessBlock(buf, m_blockSize, output, outOff);
Array.Copy(buf, 0, output, outOff + m_blockSize, bufOff - m_blockSize);
} else {
m_cipherMode.UnderlyingCipher.ProcessBlock(buf, 0, buf, 0);
for (int k = m_blockSize; k < bufOff; k++) {
byte b = buf[k - m_blockSize];
buf[k - m_blockSize] = buf[k];
buf[k] ^= b;
}
m_cipherMode.ProcessBlock(buf, 0, output, outOff);
Array.Copy(buf, m_blockSize, output, outOff + m_blockSize, bufOff - m_blockSize);
}
return bufOff;
} finally {
Reset();
}
}
}
}